The dynamics of the activity of amidases, cysteine proteinases and contents of photosynthetic pigments under effect of cold hardening (4°C) has been studied in winter wheat (Triticum aestivum L.). Changes in the activity of amidases and cysteine proteinases preceded the increase of cold-resistance, and were accompanied by the decrease in chlorophyll content in leaves. The increment of cold-resistance during hardening was accompanied by gradual decrease in the activity of proteinases and restoration of chlorophyll content. It is suggested that these changes are involved in the cold adaptation of plants.